Records v Interfaces #1099

Hi everyone,

I am trying to switch to Teal more seriously these days and I am struggling to understand how exactly records and interfaces are different. I understand that records can inherit after interfaces but interfaces can also inherit after interfaces—including multiple interfaces at the same time. Why not just instantiate an object straight from an interface instead of creating another record type?

Consider:

local interface Agent
    kind: string
    pos_x: number
    pos_y: number
end

local interface Student
    is Agent
    name: string
end

local interface GoodStudent
    is Agent, Student
    grade_highest: boolean
end

local test_student: GoodStudent = {kind = "human", name = "Borys", grade_highest = true}

The only thing I can think of that can be done with a record that cannot be done with an interface is defining a pre-initialized method. So, theoretically, to have a fully-fledged class-like object in the Python sense, for instance, you would need to do it like that:

local interface Agent
    kind: string
    pos_x: number
    pos_y: number
end

local record Student
    is Agent where kind == "human"
    name: string
    new: function(name)
end

function Student.new(name)
    ...
end

So are records just interfaces with functions and without inheritance?

What then is the purpose of function declarations in interfaces, like this:

local interface Agent
    kind: string
    print_kind: function(self.kind)
end

And then why not just have interfaces with functions and forget about records? Is method inheritance somehow problematic that we need a whole separate type just to make it possible?

I must be missing something. Help!